Heat treating process



2 Sheets-Sheet 1 Original Filed Nov. 28, 1930 /f/ f /N/ /7/ SB QNNJ YApril 25, 1933. H. A. DREFFEIN HEAT TREATING PROCESS Original Filed Nov.28, 1930 2 Sheets-Sheet 2 -/1 u oooio oooooo ooo one o oo NNM) PatentedApr. 25, 1933 UNITED STATES PATENT f orrlcE may la. nanrrnm, o1- emcaeo,rumors maar ranma rnocnss Original application iledlovember 28, 1930,Serial lo. 498,689. Divided and this application illed Jalyf 1a, fasi.Iserial nu. 550.5%. t

This invention relates to processes for heat treating metals and'monevparticularly to a process for annealing or normalizing sheetmetals, and is a division of my pending application, Serial N o.498,669,

led Nov. 28, 1930. l

An object of this invention is to provide a process for heat treatingmetal sheets or the like, as, for example, to a temperature which willetlect normalizing and thereafter quickly and satisfactoril cooling thesame in a minimum of time in a reducing-'or nonoxidizing atmosphere.

Another objectof the invention is to rovide a process of heat treatingwhich e ec'ts decided economies Ain plant structure and apparatususually employed for the purpose.

A further object of the invention is to provide means in a heat treatingprocess for rapidly cooling the treated material in a reducingatmosphere. before it leaves the treating furnace or unit.

Still another object of the invention is to provide in a heattreatingprocess for utilizing the products of combustion of the heatmgmeans in preventing the transfer by Yradiation or conduction of heatfrom the chamber in which the heating is accomplished to a coolingchamber contiguous thereto 1in such a manner that the treated materia inassmg' cooling chambe gradient which will assure satisfactory annealingor normalizing of such material in a relatively short time.

Other objects andoadvantages inherent in this invention will be morefully pointed out in the following description and accom.- panyingdrawings, in which:v

Fig. 1a is a sectional plan view of a portion of a heat treating furnaceadapted to the practice of the present processes looking from thecharging end thereof; p

Fig. 1b shows the same view looking toward the discharge end of thefurnace;

Fig. 2a is a sectional elevation of the porh tion of the furnace shownin Fig. 1a; and

Fig. 2b is a sectional elevation of that portion of the furnace shown inFig. 1b.

from the heating to the 'th rs encounters a temperature which 1s anothery Throughout the drawings like .numerals refer to similar elements.

In Figs. la and 1b are illustrated in horizontal section the majorportion of the heating chamber 10 of practice of my process. Thischamber extends to the restricting baie 11, part shown in Fig. 1b, atwhich intbegms the cooling chamber, gener y designated by numeral 12.M60

The walls and door of the` heating and cooling chambers are formed of'suitable reracto material, there being slots 14 in the floor o thechambers to permit the passage of conveyor members for the continuous 65conveyance of metal sheets, or the like, through the furnace structure.At the entrance or charging end 8 of the furnace 5 is provided avertically adjustable door 16 (better shown in Flg. and similarly 70there is provided at the-'disc arge end of the furnace an adjustabledoor 17 (Fig. 2b).

I have found it expedient and desirable to use for heat generation andsu ply the invention disclosed in my Patent o. 1,779, 75 964 issuedOctober 28, 1930, although I do not wishtoberestrictedtothesecilccombustion units except -as limited to etails thereof b the claims. A tone side of the heat' chamber adjacent the charging end 80 ereo thewallis offset at 18 to accommodate a burner 19 into and through' whichIintroduce at substantialvelocity an admixture of fuel and air, such asproducer gas and air. spaced therefrom is a restricted chamber 20,formedby the wall 21, there being a ga 22 between .one end of said walland the cgi set furnace wall 18. .At the to of the wall 21 are ports orpassages 23 see 2a) 90 formed by the partitions 23-12 extending upwardfrom the top of the wall 21. These partitions 23-a are inclinedY in such'wisev as to direct the gases ilo out of the chamber 20 into the heatingc amber prop- 95 er partially toward the entrance end ofthe eatingfurnace. The restricted chamber 20 is terminated at the end opposed tothe burner 19 by the wall 25, at the opposite side Yof a furnacesuitable for the j Opposed to the burner 19 and as' restricted chamber10,

Aformed by a partition wall 28 having partitions 28-a extending upwardfrom the wall 28. These partitions are substantially at right angles tothe major axis of the furnace structure. In alignment with therestricted chamber 27 is the burner 30 similar to burner 19, there alsobeing asimilar gap 31 between the burner and the wall 28.

These combustion units function similarly. Burning fuel mixture isintroduced, as

stated,"at substantial velocity through or- `.of the same, over, aroundand in contact with the metal sheets, for example. The

flow of gases into the restricted chamber 2() is such as to set up aninductive action whereby a portion of the products of com- 'bustion isinduced into recirculation with the gases flowing intothe restrictedchamber. Due to the inclination of the partitions 23a, the flow of gasesfrom the restricted chamber 20 is such as to enhance or aid the generalflow of gases in the fur-h nace toward the charging end thereof. Asstated, a similar action obtains in the opposed adjacent burner unitexcept that the gases flow from the vrestricted chamber 27 at rightangles to the general flow of the gases are repeatedly reheated andrecircul' gases through the heating chamber.

At the opposite sides of the furnace is provided a similar pair ofburner units generally indicated by numerals 33 and 34, being staggeredwith respect to the first described units.. The function and operationis identical with those previously described.

The side walls of the furnace are offset or inset to accommodate theburners affording easy access to the air supply ducts 35 an gas supplyducts 36 for adjustment or regu` lation.

The supply of fuel and air is preferably such that pressure is set up inthe heating chamber in excess of atmosphericv to prevent infiltration ofair. The arrangement of the ports from theirespective restrictedchambersis such as to assist or enhance the general flow ofY gasestoward and out the charging endof the heatin chamber. With the burnerunits of the c aracter described and .arranged as described, products ofcombustion will be successively picked up and recirculated in part asthey pass each heating unit, so that some of the lated in their travelthrough the heating chamber, which contributes markedly to theefliciency of operation. Also with the i an increasing temperature asthey flow toward the discharge end of the furnace since, as theirtemperatureincreases, they exercise a lesser cooling action upon theproducts of combustion. Another advantage resides in the fact that thegases during combustion thereof need not be contacted with the product,but only plroducts of combustion which eliminates t e hazardousstratiiication of air and fuel -which might cause oxidization of thesheets. It also reduces the deposit of soot, tarry substances or thelike upon the sheets. Forming a continuation with the heating chamber isthe cooling chamber 12, there being a restricting transverse wall orbaille 11, previously described, with an opening ll-a therethrough topermit the passage of the sheets and the conveying means. Leading fromthe heating chamber, preferably at the -charging end thereof, is theoutlet 40 communicatingwith the extended exterior duct 41 having the in.itial portion 41--a thereof insulated in the embodiment illustrated.This duct 41 is j located above the furnace structure and leads to anexhauster or fan 43, shown as driven by an electric motor 44 throu h themedium of a belt 45. From the an 43 leads the elbow or delivery pipe 47through the top of the cooling chamber into communication with atransversely extending box 48 having outlet .orifices 48 arranged todeliver jets of gas downwardly upon and along the surfaces of thesheets-justl rior to their discharge from the cooling c amber 12.Extending upwardly from the roof of the cooling chamber adjacent itsjuncture with the heating chamber is a plurality of vent pipes or stacks49, each of which is provided with an adjustable damper'50.

Extending transversely through the cooling chamber intermediate itsextremities` is. a plurality of air pipes 52,' terminating at each endin a manifold or header 53-54, these headers-being located on theoutside of the cooling chamber for convenience. Communicating with theyheader 53 is the duct 55 also in communication-with a motor driven fan56, whichsupplies atmos heric air to the header 53, pipes 52 andjhea er54. From the last, leads a duct 57l and a branch duct 58, the formercommunicating vwith the adjacent burner to supply air thereto,.` and thelatter to the opposed burner as` .illustrated in Fig. 1b. Similarly abranch 59 is provided to supply air to the burners on the oppositesideof the heating chamber.

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'of combustion, as stated Pipes 52 are located above the plane of travelof the sheets in the cooling chamber and in the embodiment shown begin asubstantial distance from the restricting wall A motor 60, speedreducing mechanism 61 and chain 62 together with suitable sprocketls1.furnish driving power for the shaft63. w the conveyer mechanism whichmay be of any suitable construction. y

In the practice of my process with apparatus of the type describedabove, vmetal sheets, for example, are continuously fed into the heatingchamber through the charging end thereof where theyl encounter theoutflowing heated gases. They are subjected to an increasing temperatureas they travel toward the discharge ing chamber until the desiredmaximum is reached. as, for example, from 1750o F. to 1950 F. fornormalizing. The heated gases above, flow. rearwardly from the dischargeend of the heating-chamber toward the charging end thereof, a portion ofsaid gases being picked up in their flow past each of the restrictedchambers and induced into recirculation with the incoming burning orburned gases for subsequent delivery mto the heating chamber proper.From the4 heating chamber the sheets travel into and through the coolingchamber maximum temperature.

Duringthis travel through the cooling chamberthey are submitted to thecooling action of the products of combustion which have been extractedfrom the heating chamber by the exhauster 43 through duct 41. Thesecooling gases are delivered downwardly and upon and around these sheetsas they are about to pass out of the cooling chamber. so that the flowof cooling gases is toward the heating chamber. During this tlow of thecooling gases they encounter sheets which present a generally risingtemperature asthese cooling gases progress against the direction ofmovement of the sheets and are raised in temperature to a maximum wherethey encounter the sheets at their maximum vtemperature when they arepassed from the heating chamber into the cooling chamber. This insuresagainst subjecting the sheets to a marked drop in temperature as theypass froln one chamber to the other, while at the same time theirtemperature is rapidly but more or less uniformly reduced to the desiredpoint when they leave the cooling chamber.

The heated cooling-gases, as they approach the barrier 11, in part atleast, -will then flow upwardly and back along the roof of the coolingchamber, and in part those beneath the sheets will be forced yrearwardlyalong the Hoor of the coolino' chamber for outward flow through thedischarge open-- ich carries sprockets 64 for actuation of jfrom theextracted end of the heat- 12, arriving therein at a."

ing of the furnace. The spacing of the orifices 48' permits thisdischarge of the upper rearwardly flowing hot gases.

The pipes 52 conveying air at`atmospherie temperature serve materiallyto cool or contribute to the maintenance of the cooling gases inrelatively cooled condition in their How in the cooling chamber, thuscontributing to the rapid cooling `of the sheets. At the same time theheat which is extracted from the cooling gases by the air in the pipesto preheat such air prior. to its 1 52 serves delivery to the burners,which also adds to the eiciency of operation as will be readilyrecognized by those skilled in the art." 'Ihe long travel through theduct 41 permits the substantial radiation of heat gases and products ofcombustion, so that they are very substantially reduced in temperaturebefore they are' discharged into the cooling chamber. The operation ofthe exhauster 43 may be controlled to set up any desirable pressure inthe cooling chamber, so that the pressure of the gases in the heatingchamber may -be balanced or, if desired, overbalanced by the pressure ofthe cooling gases, so that the latter serve to batile or obstruct theflow of heating gases and prevent their substantial entry into thecooling chamber. A damper 4.1-b is provided in duct 41 on suction sideof exhauster 43 for control of gas flow through ductl etl'and consequentcooling effect. In this wise, cooling gases are or may be utilized toinitiate and contribute to the rearward How of the heating gases towardthe charging end of the furnace, as describedabove. i

An increase in the quantity of the product being" handled by the furnacemay require an increase in the cooling action in thecooling chamber, inwhich event anincreased delivery of cooling gases may be required. Insuch event, in addition-` to use of the l. damper 41b,.the dampers 50 inthe vent pipes or stacks 49 maybe adjusted to permit the necessarvdischarge of cooling gases.

into the atmosphere, thereby permitting an increased delivery of suchcooling gases without increasing the amount thereof which arerecirculated in the cooling chamber.

By the construction and process described above, I am enabled to use arelatively very short length of cooling chamber with respect to theassociated heating chamber. In fact, in a furnace of approximatelyoverall length of onehundred feet I have been able I to devote seventyfeet thereof to the heating chamber and thirty feet thereof 4to thecooling chamber, while obtaining temperatures of 17 50 F. to 19500. F.in the heating chamber with'a reduction of the temperature of the sheetsin the cooling chamber before discharge thereof to from 800 F. to 1200oF., i. e. to a dull red heat or therebelow.

I find it desirable in the practiceof my process to thus heat the sheetsto the desired temperature in the heating chamber and thereafter coolthem to or below a dull red heat While maintaining a reducing ornon-oxidizing atmosphere, after which' they. may be discharged into theopen air Without danger of scaling, oxidization or other impairment. l

The advantage of being able to devote as much as possible of the lengthof aiurnace of. this character to the annealing,I normalizing or otherheating operation will bereadily appreciated by those skilled kin theart, particularly as the cost of such structures is more or lessproportional to the length thereof. Therefore, -the less such structuresare utilized for cooling the greater capacity and efliciency which willbe obtained.

It will be obvious that my process and apparatus are susceptible ofmodification and I do not Wish toV be restriced to the forms illustratedand described, except as I may be so restricted by the appended claimsproperly interpreted with respect to the prior art.

What I claim is:

1. A process of treating metal sheets consisting of passing said sheetsthrough a heating chamber, supplying heating gases to said chamber insuch Wise as to maintain a non-oxidizing atmosphere, and heating saidsheets to the desired temperature, there-- after continuing the,y travelof said sheets through av cooling chamber, and {ioWing products ofcombustion therein against the line of travel of said sheets andmaintaining a non-oxidizing atmosphere in said cooling chamber.

2. A process of treating metal sheets consisting of passing said sheetsthrough a heating chamber, supplying heating gases to said chamber insuch Wise as to maintain a non-oxidizing atmosphere and heating saidlsheets to the desired temperature, thereafter continuing the travel ofsaid sheets through a cooling chamber, and supplying products ofcombustion thereto for cooling said sheets, and forcing said products ofcombustion back againstO the advancing sheets,

.maintaining a non-oxidizing atmosphere in said coolin chamber andreducing the temperature o said sheets to a point approximating that ofa dull red heat or less.

3. A (process of treating metal sheets consisting of advancing saidsheets through a heating chamber, supplying heating gases to saidchamber in such wise asto maintain a non-oxidizing atmosphere andheating said sheets to the desired temperature, thereafter continuingthe travel of said sheets through a.cooling chamber, and supplyingproductsv of combustion thereto Vfor cooling said sheets, -said productsof combustion being flowedv back over the n advancing sheets pmore,thereafter continuing the travel of said sheets through a coolingchamber, supplying products of combustion. thereto for cooling saidsheets, and causing said products of combustion to flow against themovement of said sheets, and maintaining a `nonchamber, supplyingheatinggases oxidizing atmosphere in said cooling chamber.

5. A process of treating metal sheets consisting, of passing said sheetsthrough a heating chamber, supplying heating gases to said'chamber insuch Wise as to maintain a non-oxidizing atmosphere, and heating saidsheets to the desired temperature, thereafter continuing the travel ofsaid sheets through a cooling chamber, extracting products of combustionfrom said heating chamber, cooling and discharging the same into saidcooling chamber to cool said sheets passing therethrough.

6, A process of treating metal sheets consisting of passing said sheetsthrough a heating chamber, supplying heating gases to such chamber,flowing said. gases in said heating chamber in adirection opposite tothe direction of travel of said sheets, thereafter passing said sheetsinto and through a cooling chamber while supplying cooled products ofcombustion thereto. J l

7. A process of treating metal sheets c onsisting of passing said sheetsthrough a heating chamber, supplying heating gases to such chamber,flowing said gases in said heating chamber in a direction opposite tothe direction of. travel of said sheets, thereafter passing said sheetsinto and through a cooling' chamber whilesupplying products ofcombustion thereto'2 said products of combustion bein flowed in adirection opposite to the direction of travel of said sheets.

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8. A process of treating metal sheets consisting of passing said sheetsthrough a heating chamber,4 supplying'-vheating gases to said chamber,thereafter passing said' sheets through an extensionof said heatingchamber comprising a coolingchamber, and rsupplying cooled products .ofcombustion to against the iiow of cooled products of combustion.

Y 10. In metal treating processes which include the steps of heating themetal by combustion in a heating chamber, and passing it through acooling chamber, the method of. maintaining a desired temperature insaid cooling chamber, which comprises removing gases of combustion fromsaid heating chamber, cooling them and flowing them uniformly over the ht metal in-said cooling chamber.

11. The method of normalizing metals which comprises heating such metalsin a heating and combustion chamber free from oxidizing gases, passingsaid heated metal through a contiguous cooling chamber, extractingproducts of combustion from said heating and combustion chamber, coolingthe same, and flowing them back over the heated metals passing throughsaid cooling chamber.

12. In normalizing furnaces having heating chambers provided Withcombustion means and a contiguous cooling chamber and means forconveying materials to be normalized continuously from said heatingchamber through said cooling chamber, the method of maintaining desiredtemperatures in said cooling chamber, which comprises extractingquantities of products of combustion from said heating chamber, coolingthe same, and flowing them uniformly and continuously through saidcooling chamber in a direction opposite to the movement of materialscarried by said conveying means.

13. In a normalizing process including the steps of heating a metal in acombustion chamber and passing' it through a length of cooling chamber,the method of cooling Which comprises extracting products of combustionfrom said combustion chamber, cooling the same, and forcing them in acounter flow from the remote extremity of said cooling chamber backtoward said combustion chamber, and bailling the iniiltration of heatfrom said combustion chamber to said cooling chamber by said counterflow.

In witness whereof, I hereunto subscribe, my name this 6 day of July,1931.

. HENRY A. DREFFEIN.

